I'm planning to purchase a 36-40' boat to live on in one of the marina's in Southern Calif.. I'm new to boating and need help with some basic information. I plan to go on couple excursions per month. One of the local islands is about 165 mile round trip and the other is approx. 50 miles. I know that gas engines are far less expensive and will run far less hours between rebuilds than diesels but what is the number of hours you can run the a gas engine with "average " maintenance? Also, what is the "average" for diesels? Is there a rule of thumb for the average fuel consumption per mile for gas vs. diesels? Any help would be appreciated.